And they aren’t the only ones! You can find dozens, even hundreds, of cases where companies released source code for once-proprietary projects — and they usually benefited from it. Here are some of the more notable examples, many of which you’ll probably recognize.

1. Mozilla Firefox

Firefox wasn’t always Firefox.

Back in the 1990s, when the internet was still new and untapped, the most popular web browser was a proprietary software called Netscape Navigator. However, due to Microsoft’s successful push of the world towards Internet Explorer, Netscape Navigator had all but died out in the 2000s.

In turn, Netscape Corporation moved on and created the Netscape Communicator suite of software, which was used as the basis for the Mozilla Application suite, which would eventually become the foundation for the Phoenix browser. Due to trademark pressure, Phoenix was first renamed to Firebird and eventually renamed a second time to Firefox.

2. LibreOffice

Are you surprised to see LibreOffice on this list? Indeed, LibreOffice wasn’t always open source.

It started as a proprietary word processor back in 1985 under the name StarWriter, which was part of StarOffice by StarDivision. The company was later acquired by Sun Microsystems in 1999, who took the application and made it into an open source alternative for Microsoft Office, earning it the name OpenOffice.

3. ICQ

ICQ (“I Seek You”) is a popular instant messenger that launched back in 1996 and paved the way for the success of more well-known apps like AIM, YIM, and MSN Messenger. Surprisingly, ICQ is still used by over 11 million users worldwide.

Not much is known about ICQ’s history, but here’s what we do know: ICQ was acquired by AOL in 1998, then sold from AOL to Mail.Ru in 2010, then open sourced by Mail.Ru in 2016. Not much has come from its open sourcing, mainly because most people simply don’t know or don’t care about it.

In short, this move is the epitome of “too little, too late” and I don’t expect ICQ to explode in popularity ever again. But it is a nice move by Mail.Ru, so they do deserve some credit.

4. Blender

Open source enthusiasts often point to Blender as an example of open source software done right. It serves as proof that open source software can be as good as professional-grade alternatives, and in Blender’s case, that open source software can be better than proprietary software.

But here’s the kicker: it wasn’t always open source!

Blender began as an in-house animation application in 1995, was released as shareware in 1998, and was shut down in 2002 when the developing company went bankrupt. As a last-ditch effort, the lead developer ran a fundraising campaign and promised to open source Blender if the community raised €100,000. The goal was met in just a few months and Blender has been open source ever since.

The downside is that .NET Framework-based code can only run on machines that have the .NET Framework Runtime Environment, and for a long time this was only available for Windows. But with the framework being open sourced, it can be ported to Mac, Linux, and other operating systems, making it possible to create cross-platform apps with one codebase.

6. Live Writer

Microsoft’s foray into open source software wasn’t a one-time thing. In the years since open sourcing the .NET Framework, Microsoft has done the same for several other projects, including the beloved Windows Live Writer application.

Back in the 2000s, Microsoft acquired and integrated a company called Onfolio and all of their software products. One of these applications, Onfolio Writer, was released in 2007 as Windows Live Writer, then updated annually until its last version in 2012. At that point, development ceased.

Xamarin Studio itself was discontinued because most of its features were incorporated into Microsoft Visual Studio. All of the other software in the Xamarin SDK was released under the MIT License. They even took Mono, a Xamarin-led reimplementation of the .NET Framework that was licensed under GPL and LGPL, and relicensed it under MIT.

In other words, Microsoft took a well-known project whose parts were either proprietary or open sourced with restrictions and made most of it truly open source with no restrictions.

8. Visual Studio Code

Good text editors for programmers are hard to come by. Sublime Text is excellent but costs $70, and open source alternatives like Atom and Brackets have always had problems (e.g. poor performance, buggy updates, etc). It wasn’t until Visual Studio Code that we could have the best of both worlds.

Note: Visual Studio Code is completely separate from Visual Studio.

Visual Studio Code first launched in June 2015 under a proprietary closed source license. But after much feedback and many requests from the community, Microsoft opened it up and released it on GitHub under the MIT License. Now it’s arguably the best text editor in existence and many former Sublime/Atom/Brackets users have jumped shipped in favor of it.